1. Field of Invention
The present invention relates generally to fluid level control, and more particularly to maintaining a desired water level in a swimming pool.
2. Background Art
Swimming pools lose water everyday by evaporation from the sun regardless of the size of the pool. Pools can lose as much as one-quarter inch of water into the atmosphere on a typical day. Water loss in the pool as little a one inch typically drops the water level in the pool below that necessary for the proper use of the skimmer and circulating pump. If the water level drops below the skimmer and causes the pump to run dry, serious pump motor damage can occur. When sufficient air is drawn into the skimmer circulation system, the pump looses its prime, the impeller starts cavitation-pitting, or the pump motor over heats causing the pump motor burn-out and destruction of the pump seals. It is therefore important to be able to maintain the water level above the skimmer.
Since pool pumps are closed systems, it is possible to let the circulating pump draw (suck) make-up water already in the pool only from the bottom drain of the pool in order to temporally maintain water circulation. However, to do so, the skimmer will not collect floating debris blown into the pool. Instead, much of the debris that sinks to the bottom will be sucked up the drain and into pump collection basket. The pump basket being much smaller than the skimmer basket will eventually clog. As a result, the pump and pump motor starving for water acts as if the skimmer were starving for water. Thus, relying on the drain to do the work of the skimmer means more debris on the pool bottom and more frequent pump basket clogs. Cleaning the pool bottom and the pump basket are difficult tasks. Swimming pool owners must constantly check pool water levels, turn on the hose to fill the pool and then worry about turning the hose off before the pool overfills. Overfilling the pool can be more costly than under filling. If the water seeps under the pool deck and saturates the sub-soil, unsightly cracks or uneven deck tilting can occur. Pool owners who are away from home for more than a few days must rely upon a neighbor or a friend to add water to the pool. The benefits acquired by the use of a device to automatically maintain a constant pool level is a well-known need in the pool industry. There are several devices available to the pool owner. Some are meant for industrial use indoors and do not operate well in swimming pools due to wind and wave action. Those meant for use in swimming pools are expensive and must be installed while the pool is being built. Of those intended for use over the top of the pool deck most are expensive, bulky and marginally portable requiring that ballast water be drained out or that heavy sand bag ballasts be moved. Furthermore, few devices indicate when the desired water is achieved or indicate when the device is operating and few shut off automatically when removed from the pool to prevent swimmers from tripping over the supply hose. In addition, background art gives little consideration to the electrolytic effect of supply water moving past the valve outlet aperture and causing electrolysis resulting in pool equipment metal erosion and plaster discoloration.
Many attempts to overcome the water-level maintenance problem have been developed using ball valves, flapper valves, ball cock (toilet) valves, check valves, diaphragm valves etc. requiring lever arms, linkages, fulcrum points and precise (true) pivot points to serve as valve actuators. For example, U.S. Pat. No. 4,853,986 discloses a valve within an elastomeric nozzle having a rod protruding through the valve seat in the exit portion of the nozzle, so that bending the nozzle bends the rod to tilt a generally disc shaped washer on the valve seat to allow water to flow there through. The valve seat is an elastomeric element and, the valve washer is a one-piece metallic (non-elastic) element. The conical portions of the valve seat and washer bias together to form a true (precise) pivot point as apposed to a floating pivot, toggle-type valve. Consequently, bending the nozzle, washer and rod requires substantial torquing moments and downward ballast forces to unseat the valve against a water supply pressure. As a result, the device requires clamps, cement nails or screws to counteract against the resultant forces mentioned above. The device uses plastic jar-type float having air and ballast water contained by a lid with an eyelet in its center for attaching a cord to pull downward on the nozzle thus turning the valve on to add make-up water. As the device approaches its shut-off point, its make-up water slowly trickles down the cord and through the eyelet in the cap thus letting the water displace the air in the float and causing the float to become even heavier. Consequently, the device adds more water to the pool, changes the water level, and overfills the pool, especially when rainwater or swimmer splashes enter the eyelet in the cap on the jar. Further, the device is sensitive to rapid up and down and rocking motions due to pool water surface waves being directly coupled to water in the jar causing possible damage to plumbing. Background art is replete with true pivot points in attempts to reduce noisy and harmful chatter or “waterhammer” (i.e. rapid valve opening and closure) caused by minor fluctuations in pool water surface waves. Hence, the typical need for water baffles and plural chambers as U.S. Pat. No. 4,342,125 discusses in the Abstract; illustrates on FIG. 2; describes in the Description, and claims in dependant claim 5 (Claim of No. 3). Further, U.S. Pat. No. 4,592,098 and U.S. Pat. No. 5,655,232 have float valves operated with multiple (3) true pivot points as well as complex linkages. Additionally, each one utilizes water baffles and multi-chambered structures surrounding the float to prevent valve chatter or waterhammer as previously discussed. Also, the materials used for such structures are generally buoyant and thus require substantial cantilevers or tie-down fasteners to hold the devices near a pool deck. Further, placement next to the deck inevitably interferes with the wall climbing features of automatic pool cleaners. Like U.S. Pat. No. 4,853,986 (mentioned above), U.S. Pat. No. 4,796,650 is particularly sensitive to pool water surface wave motions because water ballast within the sealed float chamber is free to rapidly slosh back and forth within the chamber. U.S. Pat. No. 5,203,038 has the true pivot point valve movement and the same sensitivity to surface wave motions because the float is non-articulated, (i.e. ridgely coupled) to the pool water surface.